More than half of the world's population lives in cities, a percentage rapidly increasing over time. Though numerous regions such as the United States is often known for its characteristic suburban sprawl, urbanization and densification are increasing in the development of all region in the world. Using the United States as an example, the 2007 economic census found that 252 million Americans (84% of all Americans) lived in metropolitan areas up from 78 percent in 1990, and less than 40 percent in 1900. The least dense, outer suburban counties—exurbs and emerging suburbs—registered extremely low growth rates in 2010 and 2011, continuing a downward trajectory established in the late 2000s. In contrast, growth in cities and dense inner suburbs is increasing rapidly. The nation's largest core cities grew by 17 percent between 1990 and 2007, adding 6.8 million new residents. These trends are strongly accentuated in China, where 550,000,000 people currently reside in urban environments with 100,000,000 additional urban residents expected by 2020.
Urban densification provides numerous benefits to the population. It has the potential to limit the environmental impact of population growth by reducing land use, lowering emissions due to mass transit, producing more efficient resource allocation and streamlining government services, to name a few. The economic benefits to the urban citizens are also plentiful, including higher per capita income and greater opportunities. However, a 1992 study indicated that density was a consistent factor that reduced satisfaction with the urban environment. Studies generally attribute this to the social stresses of urban life, but there are indications that the physical environment plays a role as well. Dense rental housing often lacks plants and greenery when compared to areas dominated by single-family homes. In addition, apartment renters are far less likely than homeowners to have access to private land. A 2013 study of the DC tree canopy showed residents of neighborhoods dominated by rental housing tended to have less disposable income, but also did not own the green spaces around their homes.
Multiple studies show a connection between horticulture and human mental and physical health especially with regard to stress related disorders. In addition, a 2015 study found that having ten or more trees within one block of one's residence produced similar health benefits to increased income or younger age. In addition, the study found tree coverage also resulted in reported benefits to blood pressure, obesity, heart disease, and diabetes. This study can be extrapolated to show that green space and plants in general are beneficial to those living in urban environments.
Generally, designers approach the problem of alienation from the land in urban settings by designing communal green spaces. The resulting parks, urban agriculture projects, community gardens and parklets are essential to urban life. However, these efforts do not provide urban renters with a private green space to call their own. Even community gardens, where people can rent private plots tend to lack privacy and proximity to homes. In addition, they are also hard to come by. For instance, the community gardens in Seattle, called the P-Patch has a 1-2 year waiting list with 4% of the waitlist waiting four years for a gardening plot.
For many renters, the lack of private land is part of the appeal of a rental. No land means no maintenance. For others, access to planting space would make urban life far more palatable. Multiple studies show a connection between horticulture and human mental and physical health especially with regard to stress related disorders.
Urban dwellers often do have convenient space for personal gardens. Patios and balconies are often common in urban rental, apartments, condos, and smaller homes. However, these areas are generally underutilized or ignored as potential green spaces.
Garden stores are not often in urban centers. Gardeners who remain interested in planting a patio or balcony also face limited access to garden retail stores. Few garden supply retailers are willing to establish stores in city centers. As a result, urban renters must order supplies online or go to the suburbs to buy them. Renters who choose to live in walkable communities because they do not have a car have very limited options. This explains why market research shows renters, as a whole, are far less likely to invest in gardening products and supplies than homeowners.
In addition, urban environments are difficult to grow in. Urban areas may be very hot with direct sunlight & reflected sunlight & concrete heat or may be too shady for most plants due to building heights and proximity. Balconies rarely get rainwater, necessitating water transport from the apartment kitchen or bathroom in a watering can.
However, while densification is increasingly a feature of the urban environment, it has distinct environmental consequences that directly affect the plant palette of an urban renter. Dense areas produce heat islands as they store solar energy in the urban fabric during the day and release this energy into the atmosphere at night. The process of urbanization replaces the cooling effect of vegetated surfaces by imperviously engineered surfaces with different thermal properties. Furthermore, anthropogenic sources (e.g. central heating systems, air conditioning, transport, industrial processes) emit heat directly into the urban area, while buildings and infrastructure increase surface roughness that can reduce wind speeds, convective heat loss and evapotranspiration. Warm, still days reduce air quality because high temperatures and ultraviolet light stimulate the production of photochemical smog, ozone and other compounds from traffic and industrial emissions and plants.
While urban dwellers can purchase pots and limited systems for growing plants on balconies and patios, there lacks a cohesive system for use in varied urban environments. What is needed is a modular growing system for use in the varied urban environments that is capable of supporting and providing for a plurality of plants.